Transmitter and/or receiver module

ABSTRACT

The transmitter and/or receiver module comprises a dipole antenna ( 28 ) and a matching circuit ( 26 ) matching the output impedance of the module to the antenna impedance, a switch circuit ( 24 ) for switching between received and transmitted signals, a power amplifier ( 30 ) for amplifying the transmitted signal, and a low-noise receiver amplifier ( 32 ) for amplifying the received signal, wherein the matching circuit ( 26 ) and the antenna ( 28 ) are designed to provide a bandpass filter function for the module. Differential signals are provided from the transmitter power amplifier ( 30 ) to the antenna ( 28 ) and/or from the antenna ( 28 ) to the receiver amplifier ( 32 ) without conversion of the differential signals to single-ended signals.

The invention relates to a method of processing signals in a transmitterand/or receiver module, a transmitter and/or receiver module, and ansubstrate with an antenna module to be used in the transmitter and/orreceiver module. The invention further relates to a consumer electronicsdevice.

The complexity of a typical transceiver front-end is often determined bythe requirements for isolation of the receiver and transmitter, byrequirements for out-of-band filtering and by the need for conversionbetween single-ended and differential signals. To fulfill theserequirements, a balun, i.e. a balance-unbalance circuit, a switch, and abandpass filter are required in conventional modules. In addition, anantenna plus matching network is required.

FIG. 1 shows the blockdiagram of a conventional front endtransmitter/receiver circuit 2, a matching circuit 4, and an antenna 6connected to the matching circuit 4, as well as a cascade circuit 3connecting the transmitter/receiver circuit to the matching circuit 4.The transmitter/receiver circuit 2 comprises a power amplifier 8 (PA)for the transmitter function and a low-noise amplifier 10 (LNA) for thereceiver function. The cascade circuit 3 comprises a balun circuit 12(BAL) between the power amplifier 8 and a transmit/receive switch 14(SW), another balun circuit 16 between the low-noise amplifier 10 andthe switch 14, and a bandpass filter 18 (BPF) between the switch 14 andthe matching circuit 4 of the antenna 6.

The power amplifier 8 is an electronic amplifier which is designed fordelivering a significant amount of RF power to be transmitted by theantenna 6. The low noise amplifier 10 is an electronic amplifier whichis designed for amplifying weak signals received by the antenna 6. Thebalun circuits 12, 16 transform a balanced signal to an unbalancedsignal and vice versa. A balanced signal is a signal that consists of avoltage difference between two identical conductors. An unbalancedsignal is a signal that consists of a voltage difference between aconductor and the signal ground. The transmit/receive switch 14 isolatesthe receiver amplifier 10 from the transmitter amplifier 8 when a signalis transmitted or isolates the transmitter amplifier 8 from the receiveramplifier 10 when a signal is received. The bandpass filter 18 filtersthe signal spectrum in order to suppress signals outside the frequencyband of the system.

The complexity of this approach limits the minimum cost and occupiedspace as well as the performance due to the summation of all lossesoccasioned by each of the functions and mismatch losses at theinterfaces between them.

It is an object of the invention to provide a method of processingsignals in a transmitter and/or receiver module with less complexity,resulting in a lower cost.

To achieve this object, a method according to the invention ofprocessing signals to be transmitted from a transmitter modulecomprising a dipole antenna and a transmitter power amplifier foramplifying the transmitted signal, and/or to be received from a receivermodule comprising a dipole antenna and a receiver amplifier foramplifying the received signal, which method comprises a step ofproviding differential signals from the transmitter power amplifier tothe antenna and/or from the antenna to the receiver amplifier withoutconverting the differential signals to single-ended signals. It is amajor advantage of the invention that the balun is eliminated. Thisresults in a reduced size, a reduced cost and an improved performance ofthe transmitter and/or receiver module. Also, the transmitter and/orreceiver module of the invention is suitable for implementation inhybrid modules. This is advantageous in that the cost of assembly can bereduced substantially and in that the several other functions can beintegrated into the module of the invention. It is understood that saidantennas of the receiver amplifier and the transmitter power amplifiermay be the same.

To achieve the above object, a transmitter and/or receiver modulecomprising a dipole antenna, a transmitter power amplifier foramplifying the transmitted signal, and/or a receiver amplifier foramplifying the received signal is provided, wherein the antenna and thetransmitter power amplifier and/or the receiver amplifier are connectedthrough double line connections, respectively, whereby differentialsignals from the antenna are provided to the receiver amplifier and fromthe transmitter power amplifiers to the antenna without conversion ofthe differential signals to single-ended signals. Since the balun iseliminated, the transmitter and/or receiver module has a reduced sizeand lower cost.

According to a preferred embodiment of the transmitter and/or receivermodule of the invention having a balanced switch circuit for switchingbetween received and transmitted signals, the antenna and thetransmitter power amplifier for amplifying the transmitted signal and/orreceiver amplifier for amplifying the received signal are connectedthrough double line connections to the switch circuit.

According to a preferred embodiment of the transmitter and/or receivermodule of the invention, one and the same antenna is used for thetransmitter module and/or the receiver module. This antenna is balancedwith respect to the ground.

According to a preferred embodiment of the transmitter and/or receivermodule of the invention having a matching circuit matching the impedanceof the antenna and the transmitter power amplifier and/or the receiveramplifier, the antenna comprises two antenna sections which areconnected to the matching circuit at two distinct nodes thereof.

According to a preferred embodiment of the transmitter and/or receivermodule of the invention, the matching circuit and the antenna aredesigned to include the bandpass filter of the module. This reduces thecomplexity by integrating the bandpass filter function into the matchingcircuit design and the antenna design.

According to a preferred embodiment of the transmitter and/or receivermodule of the invention, the antenna is a narrowband antenna.

According to a preferred embodiment of the transmitter and/or receivermodule of the invention, the matching circuit is an integrated parallelresonant impedance matching circuit. The integration of the matchingcircuit, advantageously reduces the size of the transmitter and/orreceiver module.

The use of a narrow-band antenna in combination with a matching networkthat is parallel resonant is a preferred way of eliminating the bandpassfilter which had been required up to now.

According to a preferred embodiment of the transmitter and/or receivermodule of the invention, the combination of the impedance matchingcircuit and a dipole radiator antenna form a two-pole band pass filter,which is balanced. This leads to a further size reduction and animproved out-of-band frequency selectivity.

According to a preferred embodiment of the transmitter and/or receivermodule of the invention, the antenna comprises a stepped-impedanceprinted dipole. The impedance step results in an increased impedancebandwidth and a reduced capacitive reactance, resulting in a reducedantenna size.

According to a preferred embodiment of the transmitter and/or receivermodule of the invention, the stepped-impedance printed dipole consistsof two printed connection lines leading to two dipole bars, thedifference in line width between the connection lines and the dipolebars forming the step of the stepped-impedance printed dipole. Such anantenna is small with respect to wavelength and symmetrical with respectto ground.

According to a preferred embodiment of the module of the invention thesignal band is between 2,402 GHz and 2,480 GHz (Bluetooth® application).In general, the module is suitable for any cellular and short-rangewireless TDMA—Time Domain Multiple Access—systems, thus systems in the1-6 GHz range.

According to a preferred embodiment, the transmitter and/or receiveramplifier module of the invention is be a hybrid module. This reducesthe size of the module. Hybrid technology is a combination of differenttechnologies. In this case a silicon integrated circuit is used for theRF part and a laminated substrate and discrete surface-mounted-device(smd) components are used for the passive part of the module. Thistechnology results in a low cost and small front end with improvedperformance which will be described in detail further below.

It is another object of the invention to provide a substrate with anantenna which allows building up a transmitter and/or receiver modulewith less complexity resulting in a lower-cost product.

To achieve the above object, a substrate is provided with a dipoleantenna, the antenna comprising an impedance step arrangement. Theimpedance step arrangement leads to a more uniform current distributionresulting in more radiation.

According to a preferred embodiment of the substrate of the invention,the impedance step is realized in that the dipole antenna comprises twoconnecting parts each having a connection line and a dipole bar, whichdipole bar has a greater width than the connection line. It is anadvantage of this embodiment that a shorter antenna can be used at thefrequency of interest thanks to the widening of the dipole bars.Furthermore, the dipole bars and the connection lines as well as otherinterconnects can be provided on the substrate by a suitable technologysuch as sputtering, printing, vapor deposition. Besides, the antenna,being built up from two parts, can be designed such that only a minimumof space on the substrate is used.

In a further embodiment, a parallel resonant impedance matching circuitis present where the parts of the antenna interconnect, a major portionof the matching circuit and the antenna being embodied in oneelectrically conductive layer. The electrically conductive layerpreferably comprises a metal. It is an advantage of the embodiment thatan additional bandpass filter is not necessary. The function of thebandpass filter is integrated in the antenna plus the matching circuit,said matching circuit comprising a first and a second line which areparallel to each other and mutually coupled by the connection lines onthe one side and a capacitor on the other side, as is further indicatedin the Figures and the description.

The substrate of the invention is a good basis for building up the abovetransmitter/receiver module because the substrate with the antennaformed thereon can be used to attach the other active and passivecomponents of the above transmitter/receiver module. In other words, theswitch circuit and the transceiver device, which may be integrated intoone die, and the capacitor are placed on the substrate with the antennahaving the impedance step. If desired, the capacitor of the matchingcircuit and additional capacitors and passive components may beintegrated into a network of passive components. Alternatively, passivecomponents and interconnect lines may be integrated in the substrate,this substrate being of the multilayer type with insulating layersbetween conductive foils. Although it is preferred to provide theantenna parts at the same side of the substrate as the active and/orpassive components, these components may be provided on the reverseside. The substrate may further comprise a cavity in which any discretecomponents may be present. However, this is not the preferredembodiment, since this will increase the height of the module.

It is a further object of the invention to provide a consumerelectronics device with a receiver/transmitter module that can be usedas a plug-and-play module for any manufacturer or consumer who does nothave any antenna knowledge. This object is realized in that the consumerelectronics device comprises the receiver and/or transmitter module ofthe invention. As is well known, there is a trend towards a mobilecommunication over short distances. This trend envisages that variousconsumer electronics devices can be coupled and driven as one system.Examples of consumer electronics devices include personal computers,personal digital assistants (PALM), laptops, remote, controls, andmobile phones. The integration of the receiver and/or transmitter moduleof the invention into a consumer electronics device provides the meansfor making said communication over short distances possible. Besides,the integration of the module of the invention has the advantage thatthe interference or any other undesired coupling to other functionalcircuits in such consumer electronics device will be small in comparisonwith modules having monopole antennas. This is due to the use of thedipole antenna, which will not generate currents in the ground plane ofthe device, whereas the operation of monopole antennas depends on thegeneration of such currents. It is a further advantage of theintegration of the module of the invention that all the necessaryfunctions are integrated onto one substrate that can be placed on aprinted circuit board or inserted into the device like a modem/SIM-card.Apart from the fact that this integration onto one substrate provides amodule that can be handled easily, the module is very thin, andtherefore fits into a large variety of portable devices that are thin orbecome increasingly thinner.

These and various other advantages and features of novelty whichcharacterize the present invention are exactly defined in the claimsannexed hereto and forming part hereof However, for a betterunderstanding of the invention, its advantages, and the object obtainedby its use, reference should be made to the drawings which form afurther part hereof, and to the accompanying descriptive matter in whichand described preferred embodiments of the present invention areillustrated.

Preferred embodiments of the invention will now be described withreference to the drawings, in which

FIG. 1 is a blockdiagram of a conventional transmitter and/or receivermodule;

FIG. 2 is a blockdiagram of a transmitter and/or receiver module in anembodiment of the invention;

FIG. 3 is a plan view of a transmitter and/or receiver module in anembodiment of the invention;

FIG. 4 is a detailed view of an impedance matching circuit of thetransmitter and/or receiver module in an embodiment of the invention;

FIG. 5 is an equivalent circuit diagram of the combination of theimpedance matching circuit and the dipole radiator antenna;

FIG. 6 is a diagram of the measured radiation efficiency of the antennaplus matching network;

FIG. 7 is a diagram of the measured input reflective coefficient S11;and

FIG. 8 is a diagram of the wide-band transfer characteristic.

FIG. 2 is a blockdiagram of an embodiment of the transmitter and/orreceiver module of the invention. The module comprises a front endtransmitter/receiver circuit 22, a switch 24, and a dipole antenna 28(ANT) connected to a matching circuit 26. The transmitter/receivercircuit 22 comprises a transmitter power amplifier 30 (PA) for thetransmitter function and a receiver low-noise amplifier 32 (LNA) for thereceiver function.

The switch 24 is in cascade between the transmitter/receiver circuit 22and the matching circuit 26 of the antenna 28.

The matching circuit 26 and the switch 24 are connected through a doubleline connection 25. The switch 24 and the transmitter power amplifier 30are connected through a double line connection 27, and the switch andthe receiver amplifier 32 are connected through double line connection29. Differential signals to the antenna 28 are thus provided by thetransmitter power amplifier 30 and from the antenna (28) to the receiveramplifier 32 without conversion of the differential signals tosingle-ended signals. Therefore, the balun which was necessary in theconventional circuit is eliminated.

FIG. 3 shows an example of an implementation of the transmitter and/orreceiver module of the embodiment of FIG. 2 in a Bluetooth® transceivermodule. The power amplifier 30, the low-noise amplifier 32, thetransmit/receive switch 24, the antenna matching circuit 26, and theantenna 28 are formed on a laminated circuit board 34. A ground plane(not shown) is formed in particular printed on the back of the circuitboard 24.

The antenna 28 is a dipole antenna and comprises two printed connectionlines 36,38 leading from the matching circuit 26 to two dipole bars 40,42, respectively. The dipole bars 40,42 are connected via the connectionlines 36,38 to two distinct nodes 41,43 of the matching circuit. Thedipole bars 40,42 together exhibit a characteristic impedance. Theseimpedance values of the connecting lines and the dipole bars depend uponthe line width of the connection lines 36, 38 and the dipole bars 40,42. In this embodiment, dipole lines with a step in line width are usedwhich corresponds to a step in the characteristic impedance.

In a dipole with uniform impedance (no impedance step), the currentdecreases from a maximum in the middle to zero at the ends of theantenna. Only those parts of the antenna 28 that carry RF currentcontribute to the radiation. The impedance step results in a moreuniform current distribution, resulting in more radiation, given acertain current at the feed point. This improves the impedance bandwidthof the antenna 28. Furthermore, the wide-line (low-impedance) sectionsof the antenna, i.e. the dipole bars 40,42, lower the resonancefrequency for a given antenna size. This means that a shorter antennacan be used at the frequency of interest.

The power amplifier 30 is only capable of delivering the desired RFpower to the antenna 28 if the input impedance of the antenna 28 equalsthe value for which the amplifier 30 was designed. Likewise, the antenna28 is only capable of delivering all received power to the low-noiseamplifier 32 if the input impedance of the low noise amplifier 32 isequal to the output impedance of the antenna 28. In practice theimpedance levels do not have to be equal but should be matched to acertain degree. The matching circuit 26 improves this match over thepassband of the system.

The transmitter and/or receiver module of the above embodiment isselective as to frequency, which means that it discriminates withrespect to frequency. This offers the possibility to attenuate undesiredsignals outside the frequency band for which the system is designed, andto pass the signals in the desired frequency band, the so calledpassband.

FIG. 4 is a detailed view of the impedance matching circuit 26 havingthe above functions. It comprises, in terms of an equivalent circuit, ashunt capacitance 50 (C_2) which is a smd component in parallel to aninput of the impedance matching circuit 26. The shunt capacitance 50 isconnected on either side to a respective series inductance 52, 54 (L_3a, L_3 b), the other sides of the series inductances 52, 54 beinginterconnected through a shunt inductance 56 (L_2) which in its turn isconnected in parallel to an output of the impedance matching circuit 26.The values of the inductances 52, 54, and 56 depend on the width andlength of the printed line. The values of the inductances 52, 54, and 56and the value of the capacitance 50 are determined by the frequency bandof the passband.

The shunt capacitance 50, the series inductances 52, 54, and the shuntinductance 56 form a parallel resonant circuit which is a parallelcombination of a capacitor and an inductor. In this case the inductor issplit up into three parts so as to offer the appropriate impedance levelto the antenna. The two distinct nodes 41,43 of the matching circuit 26are located at the two ends of the shunt inductance 56.

FIG. 5 is an equivalent circuit diagram of the combination of theimpedance matching circuit and the dipole radiator antenna. The outputof the impedance matching circuit is connected to the dipole radiatorantenna 28 which comprises, in equivalent circuit terms, a seriescircuit of a first loss resistance 60 (R_2 a), a first inductance 62(L_1 a), a first capacitance 64 (C_1 a), a radiation resistance 66(R_1), a second capacitance 68 (C_1 b), a second inductance 70 (L_1 b),and a second loss resistor 72 (R_2 b).

The first inductance 62, the first capacitance 64, the radiationresistance 66, the second capacitance 68, the second inductance 70, anda second resistor 72 form a series resonant circuit. The circuit issplit in two due to the balanced nature of the antenna.

The circuit comprises two resonators, a parallel resonator, and a seriesresonator. The parallel resonator comprises the shunt capacitance 50,the series inductances 52, 54, and the shunt inductance 56. The seriesresonator comprises the first inductance 62, the second inductance 70,the first capacitance 64, and the second capacitance 68.

The circuit topology of the module shows that the combination of thedipole antenna plus the matching circuit is equivalent to a classicaltwo-pole bandpass filter. In other words, the function of the bandpassfilter is combined or integrated in the matching circuit 26 and theantenna 28, resulting in one small building block with reducedcomplexity.

In embodiment of the integrated parallel resonant impedance matchingcircuit, the parallel resonance is the result of the two lines 52,54shunted by the capacitor 50.

The integration of the module refers also to the integration of theantenna circuit 28, the matching circuit 26, the switch circuit 24, andthe transceiver 30,32 on the same (laminate) substrate 34.

FIG. 6 is a diagram of the measured radiation efficiency of the antennaplus matching network of the transmitter and/or receiver module of theabove embodiment of the invention for the Bluetooth® application, andFIG. 7 is a diagram of the measured input reflective coefficient S11 forthe transmitter and/or receiver module of the above embodiment of theinvention for the Bluetooth® application.

The radiation efficiency is a ratio of the radiated power to the poweractually entering the antenna terminal. The reflective coefficient S11is a measure for the quality of the input impedance match of a device toits nominal value. The reflective coefficient S11 is defined as theratio of the reflected wave to the incoming wave at port 1 of a two-portnetwork if port 2 is terminated without reflection. A so-called returnloss value of −10 dB corresponds to a voltage to standing wave ratio(VSWR)<2:1. This means that the impedance deviates by no more than afactor two from its nominal value (typically 50 ohms). The VSWR ratio of2:1 is a typical value for antennas in mobile phones, and the associatedmismatch loss (0.5 dB) is just acceptable for this mismatch level.

FIG. 6 relates to the embodiment having the stepped impedance printeddipole antenna and shows a comparison with a classical dipole, being theantenna without impedance step with a uniform cross-section along itslength. The efficiency diagram of FIG. 6 is not only of relevance forthe radiation efficiency of the antenna, but also for the module as awhole. Since the matching circuit and the antenna are the most criticalparts with respect to loss, the efficiency proves that the signaltransfer between the transmitter/receiver and the antenna will beadequate, although there is no balun.

FIGS. 6 and 7 also show that a more than 40% radiation efficiency incombination with a return loss level better than −10 dB is achieved overa bandwidth of 4%. This is a significant improvement over a classicalprinted dipole with the same size, which offers only 1% impedancebandwidth at a return loss level of −10 dB.

The impedance bandwidth is the frequency span (bandwidth) over which theimpedance deviation of the antenna from the nominal value is less than acertain value. The nominal value is typically 50 ohms. The bandwidth isoften specified for an VSWR value of 2:1, which means that the actualantenna impedance deviates by no more than a factor 2.

Additionally, FIG. 7 shows that a better than 10 dB return loss isachieved between roughly 2350 MHz and 2550 MHz, so over a span of 200MHz centered around the Bluetooth® center frequency of 2450 MHz. Theadvantage of the large impedance bandwidth is that the antenna will notbe disturbed easily by its environment. Small frequency shifts of theantenna due to variations in the environment will not lead to a seriousimpedance mismatch and a corresponding signal loss.

FIG. 8 is a diagram of the wide-band transfer characteristic forBluetooth®, and it shows in particular the selectivity of the bandpassfilter in the stepped impedance printed dipole of the invention. It canbe seen that the antenna additionally offers a considerable attenuationof out-of-band signals. The minimum of the attenuation lies in thefrequency band of Bluetooth®. The attenuations for the frequencies of2.4 GHz and 2.5 GHz are equal to approximately −3.4 dB and −3.3 dB at P3and P4. The attenuation for a frequency of 900 MHz is equal to −35 dBcand the attenuation for a frequency of 1800 MHz is equal to −25 dBc. Theunit dBc denotes a signal level relative to the carrier. The carrier inthis case is the signal level in the passband.

The curves shown in FIGS. 6, 7 and 8 are characteristic of a transmitterand/or receiver module in the Bluetooth® application. Comparable resultsare obtained for GSM applications in the characteristic frequency bandsof between 1710 MHz and 1880 MHz (GSM 1800) and between 1850 MHz and1990 MHz (GSM 1900), for example. The diagrams would differ only in thatother frequencies are applicable to the signal band. Obviously, the sizeof the dipole bars of the antenna would also be different.

New characteristics and advantages of the invention covered by thisdocument have been set forth in the foregoing description. It will beunderstood, however, that this disclosure is, in many respects, onlyillustrative. Changes may be made in details, particularly in matters ofshape, size, and arrangement of parts, without departing from the scopeof the invention. The scope of the invention is, of course, defined inthe terms in which the appended claims are expressed.

1. A method of processing signals to be transmitted from a transmittermodule comprising a dipole antenna and a transmitter power amplifier foramplifying the transmitted signal; and/or to be received from a receivermodule comprising a dipole antenna and a receiver amplifier foramplifying the received signal, which method comprises a step ofproviding differential signals from the transmitter power amplifier tothe antenna and/or from the antenna to the receiver amplifier withoutconversion of the differential signals to single-ended-signals.
 2. Amethod as claimed in claim 1, wherein one and the same balanced antennais used for the transmitter module and/or the receiver module.
 3. Atransmitter and/or receiver module comprising a dipole antenna (28), atransmitter power amplifier (30) for amplifying the transmitted signal,and/or a receiver amplifier (32) for amplifying the received signal,wherein the antenna (28) and the transmitter power amplifier (30) and/orthe receiver amplifier (32) are interconnected respective through doubleline connections (25,27;25,29), whereby differential signals from theantenna are provided to the receiver amplifier (32) and from thetransmitter power amplifier (30) to the antenna (28) without conversionof the differential signals to single-ended signals.
 4. A module asclaimed in claim 3 having a balanced switch circuit (24) for switchingbetween received and transmitted signals, wherein the antenna (28) andthe transmitter power amplifier (30) for amplifying the transmittedsignal and/or the receiver amplifier (32) for amplifying the receivedsignal are connected through double line interconnections (25,27,29) tothe switch circuit (24).
 5. A module as claimed in claim 3 having amatching circuit (26) matching the output impedance of the antenna (28)and the transmitter power amplifier (30) and/or the receiver amplifier(32), wherein the antenna (28) comprises two antenna sections (40,42)which are connected to the matching circuit (26) at two distinct nodes(41,43) thereof.
 6. A module as claimed in claim 5, wherein the matchingcircuit (26) and the antenna (28) are designed to provide a bandpassfilter function for the module.
 7. A module as claimed in claim 3,wherein the matching circuit (26) is an integrated parallel resonantimpedance matching circuit.
 8. A module as claimed in claim 3, whereinthe combination of the impedance matching circuit (26) and a dipoleradiator antenna (28) forms a two-pole band-pass-filter.
 9. A module asclaimed in claim 3, wherein the antenna (28) comprises astepped-impedance printed dipole.
 10. A substrate provided with a dipoleantenna, said antenna comprising an impedance step arrangement.
 11. Asubstrate as claimed in claim 10, wherein the impedance step is realizedin that the dipole antenna comprises two connecting parts each having aconnection line and a dipole bar, which dipole bar has a larger widththan the connection line.
 12. A substrate as claimed in claim 11,characterized in that a matching circuit is present where the parts ofthe antenna interconnect, a major portion of said matching circuit andthe antenna being embodied in one electrically conductive layer.
 13. Aconsumer electronics device comprising the module as claimed in claim 1.